Classification yard computer



Dec. 26, 1961 R. M. HERMES CLASSIFICATION YARD COMPUTER 3 Sheets-Sheet 2 Filed March 18, 1958 a QQQQRGSQ .mwWnN QEQUMW 3,014,658 CLASSHFHCATKUN YARD COMPUTER Richard M. Hermes, Menlo Park, Caliyfi, assignor, by

mesne assignments, to Westinghouse Air Brake Tornpany, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 13, 1958, Ser. No. 722,286 8 Claims. (Cl. 235-l) This'invention relates to an electronic computer for use in assembling cars into trains in a gravity classification yard. I

In railroad operation, it is necessary, at junctions, to disassemble incoming freight trains and to reassemble the cars comprising these trains into other trains, according to destination. This process is carried on in classification yards. In a gravity classification yard, the train to be disassembled is pushed slowly over the crest of a hill (called a hump). Each car is uncoupled at or near the crest and is allowed to roll down the hill under the influence of gravity and onto one of several tracks, with cars having the same destination being switched onto the same track. These several tracks are called classification tracks, and the portion of the yard wherein they are located is called the bowl. The first car to enter a classification track is usually stopped at the end of the track away from the hump by a skate, -a braking device fastened to the track. Subsequent cars are stopped by bumping into previously classified cars on that track.

it has been empirically determined that prior to being stopped in this manner, a car should have a velocity between two and four miles per hour. If the velocity is less than two miles per hour, the car will not couple satisfactorily with the preceding car. If the velocity is more than four miles per hour, a distinct possibility of damage to the goods being carried in the cars can be expected to occur.

All cars pass over the crest of the hump at essentially the same velocity. However, because the resistance of freight cars to rolling varies widely, the spectrum of velocities of cars arriving at their destination after having been allowed to proceed slowly under the influence of gravity will be vastly broader than the prescribed range of two to four miles per hour. Accordingly, a measure of control is injected into the system through the use of retarders or skates. A retarder is a brake mounted on the rail and capable of exerting a retarding force on the wheels of a car. The retarder may be actuated electrically or pneumatically, and both the magnitude and duration of the retarding force can be varied. it is customary to install a retarder called the rnaster retarder along the main hump and other retarders, called lead retarders, on the tracks leading to each group of five to seven classification tracks. Sometimes a retarder is installed between the master and the lead retarders. This is called an intermediate retard'er.

in some gravity classification yards the degree of braking in the various retarders is manually controlled. The retarder operator is supplied with a switching list, whichsets forth the weightand classification track for each car. From his knowledge of the number of cars already on that classification track and from his judgment of the rollability of the car-this judgment being based on the speed with which the car is approaching the retarder the operator estimates and applies the retardation necessary in the retarder so that the coupling velocity will be in the acceptable range. Since errors in judgment do occur, and since such errors are always costly, resulting either in probable damage to the goods carried in the car, or the necessity for running a locomotive over the classification track to push a car that was rolling too slowly until it connects with the preceding cars and then withdrawing Stts tent i 3,014,658 Patented Dec. 26, l'fifil L. ms 1 the locomotive, it would appear desirable to arrange a system for applying the necessary retardation automatically.

An object of this invention is the provision of a system for determining the velocity which a car should have as it leaves the retarders in order for it to be able to couple properly with preceding cars on the classification track.

Another object of this invention is the provision of a novel computer for automatically establishing the retardation required for a car in a gravity classification yard, so that its velocity is proper for coupling with the car which has preceded it.

Yet another object of the present invention is the provision of a novel, useful computer arrangement for establishing and controlling the speed of cars being assembled in a gravity classification yard.

These and other objects of the invention are achieved wherein the speed of the car after it is rolled over the hump is measured, along different sections of the track, before the car reaches the classification track section. This speed information is fed into a computer as analog voltages, as is also an analog voltage representative of the terminal speed desired for the car. From this and other data supplied to the computer in the form of the time required for the car to travel from the last retarder to the position of the cars destination on the classification track, the computer establishes the speed which the car must have when leaving the last retarder, in order that it have the proper terminal velocity. The retarders may then be actuated to slow down the car until the difference be tween actual and computed velocity is zero. The'velocity of the car will then be the required value for successfully coupling with the preceding cars.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 shows the track layout for a typical gravity distribution yard which is shown along with identifying symbols to assist in an understanding of this invention;

FIGURES 2 and 3 are block schematic diagrams of an arrangement of an embodiment of this invention; and

FIGURE 4 is a timing arrangement and diagram for the invention.

FIGURE 1 shows a typical classification yard layout for which this invention is suitable. This includes the track section after the hump, which is identified byv the label tangent track calibration section 10. This is followed by a section of track, along which are distributed the retarders. This section of track is identified as the master retarder section 12. A first radar speed observer i4 is positioned alongside this track section. The radar speed observer is a commercially purchasable item commonly employed by police departments in measuring the speed of a car. The radar speed observer will establish as its output a voltage representative of the speed of the freight car as it is passing through the tangent track calibration section.

'After the master, retarder track section 12, there is a curved track calibration section 14. This is followed by a track section to, wherein the lead retarders are positioned. For observing the speed of the car on the curved track calibration section and as it enters the lead retarder track section, a second radar speed observer 16 is positioned adjacent these track sections. The velocity of the car as it leaves the lead retarder will be known as the exit velocity V T he track section following the lead retarder section to will be designated as the third section 18 and extends from the lead retarder track section a distance to where the classification section begins. Each classification track will have a second track section 20 which extends from the third section for the distance required for the car to pass the curved section of the classification track. A first track section 22 extends to the location at which a car must have the terminal velocity designated as V which is equal to 3+1 miles per hour.

The true law governing the rollability of freight cars may be derived from Newtons conservation of energy equation. A differential equation involving many terms may be set up, which will include, for example, the velocity of the rolling car, the time rate of change of that velocity, the slope of the track on which a car is rolling, and the gravitational constant. However, from experimentation it has been determined that many of the terms in the initially established differential equation are so small as to be negligible and, accordingly, a desired approximation to the laws governing the rollability of freight cars may be expressed as where g is the gravitational constant, V is the time rate of change of the car velocity, V is the velocity of the rolling car, a is the slope of the track on which the car is rolling, and K has two values, one of which is K,;, the viscous friction coefficient on straight track, and the other of which is K the viscous friction coefiicient on curved track. Also, K is different for difierent cars.

In accordance with the above equations, in order to control the coupling speed of a freight car in a typical yard, such as that shown in FIGURE 1, it is necessary to measure K, on a straight calibration track and to measure K, on a curved calibration track. It is also necessary to know where the car is to couple on the classification track. After deriving this information, then in order to determine what the velocity V should be with which the car will leave the lead retarding track section 16, it is only necessary to integrate the equation backwards, using V and K for the first track section to obtain the velocity V This is the velocity which the car should have just as it leaves the second track section 20 and enters the first section. V and K are then substituted in the above equation, and it is integrated backwards in order to determine the velocity V which the car should have when it enters the second track section 20. Finally, backward integration is then used again, employing the values of V and K, in the equation, to determine the velocity V with which the car must exit from the lead retarder.

In these three integrations, the distances and the slopes of the second and third track sections and the slope of the first section are all constant. The length of the first section varies, depending on the number of cars already thereon. This variable length may be readily simulated.

FIGURE 2 is the portion of the computer which is an embodiment of this invention for determining the average values of K and/or K The input to this computer will be from the first radar speed observer 14 while the car is rolling over the tangent track calibration section It The second radar speed observer 16 will provide an input to the computer at the time the car is moving through the curved track calibration section t4.

The computer 'for establishing the correct velocity V which a car should have after leaving the lead retarder section of the track, actually is comprised of two portions. The first, shown in FIGURE 2, is employed to establish the average values of K and/or K The second portion of the computer, which computes the voltage representative of V is shown in FIGURE 3. The circuits shown in FIGURES 2 and 3 employ relays, in the course of the performance of the computations which are operated in a time sequence. These relays, besides a reference numeral, will have a letter adjacent to the relay coil, which corresponds to a letter shown on the time diagram in FiGURE 4. Thus, the time when a relay is operated relative to other relays may be determined by looking at FIGURE 4 and then at the letter or letters adjacent the relay coil.

FIGURE 4 also shows an arrangement for actuating the relays in the required time sequence. When a train enters the tangent track calibration section 10, a track switch 30, shown in FIGURE 5, is closed momentarily. This enables power to be applied from a source 32 to a motor 34. The motor starts turning a shaft on which there are mounted a plurality of cams A through N, each of which can close a set of contacts respectively designated by the letters A through N during an interval and occurring in a sequence as shown in FIGURE 4 by the corresponding letters. When these are closed, they energize the relay having associated therewith the same letter. Thus, as soon as motor 34 is operated, the A and N cams close switch contacts M", N", which applies an energizing potential to the relays 31 in FIGURE 4- and 83 in FIGURE 2. This will close the relay contacts 31, associated with the relay, whereby power is applied to the motor 34 during the N computing interval.

The arrangement for the computer which is shown there solves the equation below for K It will be recognized that this is the previously shown equation, with all terms transposed to one side thereof. Referring now to FIGURE 2, when a train enters the tangent track calibration section 10, it trips a track switch, which as it may be sen in FIGURE 4 causes the motor 34- to start the operation of the cams and switches. The relay S3 is closed during this first interval, designated as A. It can then apply the output from the first radar speed observer 14 to the input to the computer comprising a multiplier circuit 40 and a differentiation circuit 42. The output of the first radar speed observer will be a voltage proportional to the velocity of the car in the first track calibration section. After an interval sulficiently long to enable the difierentiating circuit 42 to become quiescent after the application of the input voltage, the relay 43 is operated during B time and its contacts connect the output of the differentiating circuit to a potentiometer 44, which has its movable arm positioned a distance proportional to from one end so that the output of the differentiating circuit, representative of V, is multiplied by a factor E The potentiometer output corresponding to the product is applied to a summing amplifier 46. A second input to the summing amplifier is derived from a potentiometer 48, connected across a battery 50. The slider arm of the potentiometer is set to provide an output potential corresponding to the negative of the slope a of the tangent track calibration section. This slope is a constant, and thus can be represented by the fixed potentiometer output voltage. A relay 52, which is operated during A time, applies the output of potentiometer 48, which represents o' to the summing amplifier 46.

A third input to the summing amplifier 46 is the output of the multiplier circuit 40. It should be noted that the slope input to the summing amplifier is in reverse polarity to the other inputs, and therefore effectively is subtracted from these other inputs. The output of the summing amplifier 46 is applied to a high-gain amplifier 54. The high-gain amplifier output is fed back as a second input to the multiplier circuit 40, to multiply the input voltage V received from the first radar speed observer 14. Since for any given set of conditions, the only variable in the equation being solved by the loop described is K, the output of the high-gain amplifier is a voltage whose value is representative of the term K. This is an instantaneous value, and the remainder of the computer shown in FIGURE 2 is employed to find'an average value of K.

After the elapse of time suflicient to enable the loop to stabilize, the voltage representative of K is fed to an integrator circuit 56 through the contacts of a relay 58, which is operated during C time. A relay titlhas normally closed contacts which serve to ground the integrator output when computation function is being done in order that the integrator be reset for each computation. The relay 60 is operated during C time, opening its contacts and enabling the integrator circuit to function. The output of the integrator circuit 56 will be a voltage representing the integral of K for the interval of time during which the voltage value of K is applied to the integrator 56.

The output of the integrator 56 is applied to a multiplier circuit 62. A second input to the multiplier circuit is obtained from circuitry which generates a voltage representative of the value This is done by applying a voltage from a constant voltage source 64 to a time integrator circuit 66 for the same interval of time as the voltage representative of K is applied to the integrator circuit 56. To efiectuate this, a relay 68 has its contacts closed to apply the constant voltage from the source 64 to the integrator circuit'fi during C time. The output of the time integrator circuit 66 is a voltage which is representative of the time interval T. It should be noted that the time integrator circuit 66 also has connected across its output a relay 7ii,'-the contacts of which ground the output of the integrator circuit, ex-

cept during C time. Thus, the resetting of the time integrator circuit 66 is assured during all thetimes in which it is not used for computation. The voltage T is applied to a phase-inverter circuit 68, which produces a voltage representative of the reciprocal of its input. The output of the phase inverter 68, comprising the term is applied to the multiplier circuit 62 to multiply the voltage representing the time integral of K, or fKdt. Therefore, the output of the multiplier circuit will be an average value of K for the tangent track calibration section.

The multiplier output is applied to two positional servos, respectively 72, 74. During C time, a relay 76 is operated. The relay 76 has two contacts, 76 and 76 Contact 76 closes to permit power to be applied to one winding '78 of a servo-follower motor, and the contacts 76 enable the error voltage output of the positional servo 74 to be applied to the winding $0 of the servo. The servo-follower motor is thus enabled to rotate to eliminate the error voltage and to thereby move the arm of a potentiometer $2 to a position representative of the value of K for the tangent track calibration section. At this time, the N computing time interval is completed and the relay 31 is made inoperative. This opens contacts 31, and motor 34 stops.

When the car reaches the curved track calibration section 14, a track switch 33 (FIGURE 4) is operated, starting motor 3d until. the N computing interval is begun. A relay 84 is energized during D time, and its contacts close and connect the output of the second radar speed observer 16 to the multiplier circuit 40 and diiferentiat- 6 ing circuit 42. Relay 43 is operated during E time, to enable the output of the differentiating circuit to be applied across the potentiometer 44, whose output is representative of the product A relay 86 is also closed during D time, whereby a fixed voltage whose value is representative of 0' or the slope of the curved portion of the track, is obtained from potentiometer 88, connected to a potential source 96. This is applied to the summing amplifier 46 to be subtracted from the other inputs to the summing amplifier.

The output of the high-gain amplifier 54 is again applied to the integrating circuit 56 through contacts of relay 58, which this time is operated during F time. Simultaneously, the relay 68 is operated to enable the time integrating circuit 66 to produce a value of voltage representative of dz. This is inverted by the phase-inverter 68 and is then applied to the multiplier circuit 62. Relays and 74B are operated during F time. A relay 92 is also operated during F time, whereby its contacts 92 can apply AC. power to one Winding 94 of the servofollower motor and the output of positional servo can be applied to the other winding 95 of the servo-follower motor over the relay contacts 92 This enables the servo-follower motor to position the slider of potentiometer 98 to a position established in response to output from the positional servo No. 1, which is representative of K for the curved section of the track.

Attention is now directed to FIGURE 3, which is a blockdiagram of the portion of the computer utilizing the information derived by the circuit shown in FIGURE 2 for computing the required exit velocity.

Y In order to effectuate the remaining calculations, it is necessary to make in the previously shown equation the substitution W as as at which is equal to BTs :18 here represents an increment of distance along the track. Substituting this in the equation provides niques, the independent variable S is made proportional to real time; thus, S is proportional to t, or S equals AT,

where A is a constant. Therefore, the equation which is to be solved by the computer shown in FIGURE 3 will be It was pointed out previously that the required coupling velocity is 311 mile per hour. A voltage V,, representative of this required coupling velocity, is derived from a potentiometer 1%, which is connected across the potential source 102. During G time, a relay 1% is operated to close its contacts to apply the voltage representative of the desired coupling velocity V, to a differentiating circuitlil and to a multiplier circuit 1%. The output of the differentiating circuit is also applied to the multiplier circuit. The output of the multiplier circuit is a product representative of sliding arm is established at a position so that the output will be the product of a following summing amplifier 116 will be a voltage whose value is equivalent to A second input to the summing amplifier during H time is a negative voltage representative of the slope of the first section of track 22. This voltage U is applied from a potentiometer 112 over the contacts of a relay 114, which is operated during H time, to the summing amplifier 116. Another input to the summing amplifier 3.1.6 is a voltage representative of the product V K This is derived by applying across the potentiometer 82 (previously shown positioned at K in FIGURE 2) the voltage V,, which is applied to the input of the differentiating circuit 196. A relay 118 is operated during H time, and its contacts enable application of the voltage K V, to the summing amplifier. The output of the summing amplifier is applied to a high-gain amplifier 120. The output of the high-gain amplifier 120 is fed back to the input of the ditferentiator circuit 106 to close the loop.

When the loop including the structure just described reaches its stable state, the output of the high-gain amplifier 120 will be avoltage which effectively represents the desired velocity V This is applied to the positional servo 124. This voltage drives the positional servo 124 to a position determined by its amplitude. A relay 126 is energized at H time and enables a voltage representative of the distance of the first track section 22 to be obtained from a potentiometer 123, which is connected across a potential source and to be applied to a delay multivibrator B8. The delay multivibrator 130 is a well-known circuit of the type which will provide an output voltage which has a duration proportional to the amplitude of the input voltage. It should be noted that in order to enable the delay multivibrator to respond to the voltage from the potentiometer "E28, a relay 132 is energized during H time and enables an operating potential to be applied from a source 134 to the delay multivibrator 1.3% The output of the delay multivibrator 133 is used to enable a relay 136 to be operated for a time determined by its duration.

One of the pairs of contacts 136 of the relay 136 a plies A.C. power to one winding 138 of the servomotor. A second contact 136 applies output from the positional servo 124 to the other winding 1 56 of the control phase of the servomotor. The follow motor is thus enabled to establish a position for the movable arm of potentiometer 142, so that with a fixed voltage applied across it the output derived from the potentiometer will be a voltage representative of the velocity V which the car should have when it enters the first section of the track. Of course, a scaling voltage from a potential source 143 must be applied across the potentiometer 142.

At this time, it should be noted that the voltage representative of the distance of the first track section, which is derived from the potentiometer 1225, is altered to correct for the shortening of this first track section each time a car enters by employing a track switch 144, closed by the car wheels, which applies a potential from a source we to an incremental motor 143. This motor moves the shaft of the potentiometer 128 an increment to reduce the value of the voltage derived therefrom by an increment representing the reduction in the length of the third section of track.

The output of potentiometer 142, V is now fed bacir into the loop in place of he voltage V,. During I time, a relay lfiilis energized, thus enabling its contacts to apply the output of the potentiometer 142 to the differentiator circuit 10s. During I time, a relay 152 is also closed and its contacts apply a potential from a potentiometer 154 during 1 time to the summing amplifier 116. This potential is representative of the value of the slopea of the second track section.

This time, since the track section is curved, a relay 156 is energized during K time, connecting the potentiometer 98 into the loop (shown previously in FIGURE 2). Relay 156 is energized during K time, and its contacts apply a voltage V K from potentiometer 98 to the summing amplifier 116. Again, the output of the high-gain amplifier is applied to the positional servo 124. A relay 158 is energized during K time, and its contacts close to apply a voltage from a potentiometer 169 to the delay multivibrator input. The voltage derived from potentiometer 160 represents the length of the second track section. The relay 132 is also energized at K time, whereby the delay multivibrator operates relay 136 for a time proportional to the length of the second track scction. Thus, potentiometer 142 is enabled to be positioned to provide a voltage representative of the velocity V required for a car as it enters the second track section, in order that its terminal velocity be the required 3:1 mile per hour.

The backwards integration is performed once more, in order to derive the velocity V with which the car must leave the lead retarder section of the track, or with which the car must enter the third section of the track 18, to have the desired terminal velocity. This time, during M time, a relay 166 is operated to enable the application of the slope representative voltage--a to be derived from a potentiometer 162 and to be applied to the summing amplifier 116. This 0 slope voltage is the slope of the third section of the track 18. Relay 156 is also closed during M time, as is also relay 113, which enables the voltage representative of K, to be applied to the summing amplifier.' Thus,'the positional servo .124 will receive a voltage, the value of which represents car velocity at the termination of the third track section.

A relay 16% is operated during M time, thus applying a voltage from the potentiometer 166, which is proportional to or representative or" the distance of the third track section. Delay multivibratcr 136 is enabled to hold operative the relay 136 during the time interval proportional to this input voltage, whereby the voltage derived from potentiometer 14-2 is proportional to the velocity V,,, which a car should have when it leaves the lead retarder track section 16 to enter the third track section 13. At this time the N time interval terminates and motor 3-iceases operation at the end of the computing cycle.

The value of this voltage may be displayed upon a meter to be compared side-oy-side with the value of the voltage which is derived by operation or" the second radar speed observer as it scans the car in passing through the lead retarder track section 16. The retardation operation can be maintained until the values of these voltages are identical. Otherwise, if preferred, these voltages may be applied to a comparator circuit 170 via track switches 172, 174, which may be energized when the car enters the lead retarder section of the track. The output of the comparator will be employed to operate a lead retarder. When the comparator output is zero, the lead retarders no longer will retard the car, and it should then have the computed exit velocity, which is required in order that its terminal velocity be correct.

Where there are a plurality of distribution tracks, a duplicate set of the relays 126, 15%, 1'54 as well as the associated potentiometer and potential sources are required for each distribution track. When there is switched in the proper distribution track to receive a car coming from over the hump, the switchman can simultaneously actuate switching apparatus to select the proper set of relays and potentiometers.

The circuits represented by the blocks are well-known analog circuits. These are all found described and shown, for example, in the text Electronic Instruments, by

9 Greenwood et al., published by McGraw-Hill Book Company in 1948. The servo apparatus is also Well known and described in this text. The manner of interconnecting all this apparatus is also known and well within the skill of the technician in the art.

There has accordingly been described hereinabove a novel, useful, system for determining the proper speed with which a railroad car should leave the lead retarder section of a track in a distribution yard, in order that its terminal velocity be correct for coupling.

1 claim:

1. An analog computer for establishing the average value of K, the viscous coefiicient of friction for a moving land vehicle in the equation 1 dV g dT +KV o'() a is a constant where g is the gravity acceleration constant,

is the acceleration of the vehicle, V is the velocity of the vehicle, and is the slope of the surface on which the vehicle is moving, said computer comprising means to establish a first voltage representative of the velocity V of said vehicle, a multiplier circuit having two inputs, a differentiating circuit, means to apply said first voltage to one of said multiplier circuit inputs and to said differentiating circuit input, potentiometer means to which said differentiating circuit output is applied to multiply said differentiating circuit output by a value representative of a summing amplifier having three inputs, means to respectively apply output from said multiplier circuit and said potentiometer means to a first and second of said inputs, means to establish a voltage representative of the negative of the slope on which said vehicle is rolling, means to apply said slope representative voltage to said summing amplifier third input, a high-gain amplifier to which output from said summing amplifier is applied, means to apply output from said high-gain amplifier to the second input of said multiplier, means to integrate the output from said high-gain amplifier for a predetermined time interval, means to generate a voltage representative of the reciprocal of said predetermined time interval, means to multiply the output of said means to integrate by said voltage representative of the reciprocal of said time interval to obtain as a product a voltage representative of the average value of the viscous coefficient of friction.

2. An analog computer for computing the velocity which a moving vehicle should have at a first position in order to have a desired terminal velocity at a second position which is ata distance from the first position, in accordance with the equation where a is a constant,

g isthe gravity acceleration constant, 1 V is the velocity of the vehicle,

friction,

velocity, a differentiating circuit, means to apply said first voltage to said differentiating circuit input, a multiplier circuit having a first input to which said differentiating circuit output is applied and a second input to which said first voltage is applied, first potentiometer means to which said multiplier circuit output is applied to multiply said output by the constant value means to establish a voltage representative of the negative of the slope of the surface on which said land vehicle is moving, second potentiometer means to mul tiply said first voltage by the average viscous coefiicient of friction of said vehicle, a summing amplifier having three inputs, means to respectively apply said first and second potentiometer means outputs and said slope representative voltage to said respective summing amplifier three inputs, a high-gain amplifier, means to apply said summing amplifier output to said high-gain amplifier input, means to apply said high-gain amplifier output to said differentiating circuit input, means to establish a time interval representative of the distance between said first and second positions, integrating means having its input coupled to receive output from said high-gain amplifier, and means to energize said integrating means for the time interval established by said means to establish a time interval whereby the output of said integrating means is a voltage representative of the required velocity at said first position.

3. An analog computer as recited in claim 2 wherein the path traveled between said first position and said second position includes a curved portion and a straight portion, said means to establish a voltage representative of the negative of the slope of the surface on which said land vehicle is moving includes a means to establish a second voltage for the straight path slope and a means to establish a third voltage for the curved path slope; said second potentiometer means to multiply said first voltage by the average viscous coefiicient of friction of said vehicle includes, a straight-path potentiometer means to multiply said first voltage by the average viscous coeiiicient of said vehicle for a straight path, and a curvedpath potentiometer means to multiply said first voltage by the average viscous coefiicient of friction of said vehicle for a curved path; said means to establish a time interval representative of the distance between said two positions includes means to establish a first time interval representing the length of said straight path, and means to establish a second time interval representing the length of said curved path; and there are included means for concurrently applying said second voltage and the output of said straight-path potentiometer to said respective summing amplifier inputs while said integrating means is energized for said first time interval, means for con currently applying said third voltage, the output of said third curved-path potentiometer to said respective summing amplifier inputs and the output of said integrating straight path and over a curved path and to establish fifthv and sixth voltages representative of said curved I entiating circuit output to alternate said output, a summing means having three inputs and an output, said multiplier circuit output and said potentiometer means output being connected to two of said summing means inputs, a high-gain amplifier coupled between said summing means output and the other of said multiplier circuit inputs, an integrating circuit having its input connected to said other summing means inputs, means to enable said integrating circuit for a predetermined time interval, a first adjustable potentiometer, a second adjustable potentiometer, means for applying said fifth and seventh voltages respectively to said one multiplier circuit input and said third summing amplifier input, means for adjusting said first adjustable potentiometer to provide a resistance value representative of the output voltage of said integrating circuit, means for applying said sixth and eighth voltages respectively to said one of said multiplier circuit inputs and to said third summing amplifier input, means for adjusting said second adjustable potentiometer to provide a resistance value representative of the output of said integrating circuit, means for applying said first voltage across said first and second variable potentiometers, whereby the output of said first variable potentiometer represents the product of said first voltage and the average viscous coefficient of friction of said vehicle along a straight track section, and said second variable potentiometer output represents the product of said first voltage and the average viscous coefficient of friction of said vehicle along a curved track section, and means for selectively applying the outputs of said first and second variable potentiometers to said summing amplifier input.

5. A system for establishing the proper release velocity for a freight car in a gravity classification yard to secure proper coupling velocity comprising first and second otentiometers each having a fixed resistor and a slider movable along said resistor; means for placing said first potentiometer slider in a position representative of the viscous coefficient of friction for a car rolling on a straight section of track, means for placing said second potentiometer slider in a position representative of the viscous coefiicient of friction for a car rolling on a curved section of track, means for establishing a voltage representative of the proper coupling velocity, means to establish different voltages representative of the negative of the slope of each section of straight track and to the length of each section of curved track extending from the point in said classification yard at which said proper coupling velocity is required to the point in said classification yard at which the proper release velocity is established, a differentiating circuit, a multiplier circuit connected to receive as inputs to be multiplied the output of said differentiating circuit and the input to said differentiating circuit, first potentiometric means to multiply the output of said multiplier circuit by a constant proportional to the negative of the reciprocal of the acceleration of a body due to gravity, a summing amplifier having three inputs, means for applying the output of said first potentiometric means to said summing amplifier first input, means for applying the voltages representative of the negatives of the slopes of the straight and curved track sections in sequence extending from the point in said classification yard at which said proper coupling is required to the point in said classification yard at which said proper release velocity is established, means for connecting the input to said differentiating circuit across said first and second potentiometer resistors, means for connecting one of the first and second potentiometer sliders to said third summing amplifier input in accordance with whether the slope representative voltage being applied to the second summing amplifier input is a curved or straight track section, means to couple the output of said summing amplifier to the input of said differentiating circuit, means to apply for a limited time said voltage representative of a required coupling velocity to the input of said differentiating circuit, timing means to establish in se quence time intervals respectively representative of the lengths of each of said track sections extending from the point at which said proper coupling velocity is required, integrating means to which said summing amplifier output is applied, means rendered operative responsive to said timing means to successively enable said integrating means during said sequence of time intervals, and means to apply the output of said integrating means to the input of said differentiating circuit after a first of said time intervals whereby at the end of said time intervals the output of said differentiating means is a voltage representative of the proper release velocity for a freight car.

6. An analog computer for determining in a gravity classification yard, the release velocity of a car when it leaves a section of track equipped with retarders, in order to have the proper coupling velocity when it is stopped by a preceding car on a classification track, the distance between said retarder equipped track and said point of proper coupling velocity being made up of straight and curved track lengths, a straight-track length extending to the next curved-track length, a curved-track length extending to the next straight track length, said computer including means for measuring the velocity of a car on a straight-track section and establishing a first voltage representative thereof, means for measuring the velocity of said car on a curved-track section and establishing a second voltage representative thereof, means for establishing a third voltage representative of the slope of the straight-track section on which said car velocity is measured, means for establishing a fourth voltage representative of the slope of the curved-track section on which said car velocity is measured, a first and a second potentiometer means each having a resistor and a slider movable thereover, means for respectively moving said first potentiometer slider to a position representative of the average value of the viscous coefficient of friction of said car for straight track and for moving said second potentiometer slider to a position representative of the average value of the viscous coefiicient of friction of said car for curved-track respectively responsive to application of said first and third voltages and to application of said second and fourth voltages, means to establish a fifth voltage representative of the proper coupling velocity, means to establish a different voltage representative of the slope of each track length between said point of proper coupling velocity and retarder equipped track, means for establishing a different time interval representative of the length of each of said different track lengths, and a release velocity computer including a differentiating circuit having an input and output, a multiplier circuit having an output and two inputs, one of which is connected to said differentiating circuit input the other of which is connected to said differentiating circuit output, means to multiply said multiplier circuit output by a constant, a summing amplifier having three inputs and an output, one of said summing amplifier inputs being connected to the output of said means to multiply, a high-gain amplifier coupling said summing amplifier output to said differentiating circuit input, means conmeeting said first and second potentiometer resistors to said differentiating circuit input, integrating means having an output and an input, said integrating means input being coupled to said differentiating circuit input, means for enabling said integrating means to integrate for different time intervals provided by said means for establishing different time intervals in a sequence determined by the sequence of track lengths going from said point of proper coupling velocity to said retarder-equipped track, means for successively applying to a second one of said summing amplifier inputs each of the voltages representative of the slope of one of said track lengths while said integrating means is successively energized during the corresponding time interval representative of smgsas each of said track lengths, means for connecting to a third one of said summing amplifier inputs the slider of the one of said first and second potentiometers as determined by Whether the track length for which sloperepresentative voltage is being applied to said summing amplifier is straight or curved, means for applying said fifth voltage to said difierentiating circuit input during the time interval of said first energization of said integrating means, and means for thereafter applying the output of said integrating means to said differentiating circuit input.

7. An analog computer as recited in claim 6 wherein said means for respectively moving said first and second potentiometer sliders includes a multiplier circuit having two inputs and an output, a difierentiating circuit having an output and an input connected to one-of said multiplier circuit inputs, potentiometer means to which said differentiating circuit output is applied to multiply said output by a constant, a summing amplifier having three inputs and an output means, for applying said multiplier circuit output and said potentiometer means output respectively to a first and second of said summing amplifier inputs, a high-gain amplifier having said summing amplifier output connected to its input and its output connected to said other of said multiplier circuit inputs, an integrating circuit connected to said high gain amplifier output, means to enable said integrating circuit to integrate the output of said high-gain amplifier for a preset time interval, means for generating a M- voltage representative of the reciprocal of said time interval, and means for multiplying said integrating circuit output with said voltage representative of the reciprocal of said time interval, and means for establishing a shaft rotation proportional to output from said means for multiplying.

8. An analog computer as recited in claim 5 wherein said integrating means includes a positional servo having its input coupled to said differentiating circuit input, a follower motor having a control Winding, a potentiometer having its slider driven rotatably by said follower motor, and a relay having normally open contacts to which said positional servo output and motor control winding are coupled, and said means to enable said integrating means to integrate for different time intervals includes a variable delay multivibrator having its output coupled to said relay to render said relay operative for a time determined by the amplitude of voltages applied to said delay multivibrator input.

References fitted in the file of this patent UNITED STATES PATENTS Darlington Jan. 10, 1950 Lehmann Apr. 14, 1953 OTHER REFERENCES 

